Steel casing pipe is often percussively rammed horizontally under expressways, boulevards, railways and other heavily traveled roadways to provide passage for buried utilities such as potable water, sanitary sewer, storm sewer and natural gas pipelines. The steel pipe is most commonly used as a jacket for the carrier pipe and therefore allows multiple utilities to pass through a single crossing pipe. The process of pipe ramming, a well-accepted method within the trenchless technology family of construction processes, allows said steel casing to be placed beneath an active roadway without the undesirable consequences of shutting down the flow of traffic.
As the crossings are often shared by multiple mainline utilities, the casings may be large in cross sectional diameter; 36 inch to 72 inch diameter is fairly common and casings up to 120 inches have been installed, though less frequently. The percussive rammer typically has a cross section that is also cylindrical, like the pipe. The rammer is smaller, between 20% and 75% of the casing diameter. Adaptation must be made between the rammer and the casing face to transfer the percussive load. When the hammer diameter is small compared to the casing diameter, the adapter design and handling becomes a challenge. This is especially true in casings over 48″ diameter.
Thus, an adapter must be able to transfer force from the rammer to the casing. Components of such an adapter, especially when they are segmented, may be difficult to handle. The components must be assembled into the inside of the distal end of the casing such that the percussive blows of the hammer will be transmitted to the casing and drive it through the soil under the roadway. When multiple adapters are needed for large casings, these problems multiply. Components may need to be welded to the casing in order to ensure a proper connection during the ramming process. Welding takes time and is expensive. The present invention seeks to overcome these challenges.